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I'm trying to install a new light switch from a plastic one to a metal one.

I don't have a ground wire nor is the back box grounded.

Do I need to connect it to a ground?

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  • plastic one to a metal one ? what is plastic ? – Alaska Man May 26 '20 at 18:43
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    Does this answer your question? Is a ground required when replacing an old single pole single throw switch? – isherwood May 26 '20 at 18:44
  • "I'm trying to install a new light switch from a plastic one to a metal one." Can you clarify what that means please. – Alaska Man May 26 '20 at 18:54
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    You have to state your location as regulations vary and this is an international site. In the UK you must not install a metal switch on an ungrounded circuit, and a warning label must be placed at the consumer unit if any circuits are ungrounded. – Owain May 26 '20 at 19:00
  • Can you post photos of the inside of the back box please? – ThreePhaseEel May 27 '20 at 0:38
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Assuming you are in North America: When boxes were steel and the wiring was run with metal conduit or BX cable (flexible metal armoring wrapped around the wires instead of a plastic or fabric jacket), grounding was done via the metal-to-metal contact of the switch to the box, the box to the conduit and the conduit to the breaker panel, which was itself bonded to ground. If you have removed a steel box and replaced it with a plastic one, but the wiring is still in the BX cable, then you can get a fitting for attaching the BX to the box that allows you to attach a ground wire (grounding locknut). But technically, it would not meet current code, because the old BX cable no longer meets the requirements for continuous grounding. NEWER versions, now called "Type AC" cable (for Armor Clad) have a different design that meets code grounding requirements.

For a while, code allowed for switches to not have any ground connection though, so you would have NM (Non Metallic) cable without a ground wire used on them. In that case if you are replacing like-for-like, you can ignore the ground connection on a new switch, there is a Code exception under article 404.9(B) allowing for that.

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Ungrounded switches were common until a few decades ago. If you're simply replacing a basic switch with a basic switch, you do not need to run a new ground wire.

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